Plan Document Reviewer

Purpose: Catch plan gaps BEFORE they survive into implementation. Bad task decomposition, missing steps, and spec misalignment cost 10x more to fix during implementation than during review.

When to Dispatch

After Phase 4 (design) writes .planning/PLAN.md and before Phase 5 (implement) begins.

Phase 4: Design → PLAN.md written → user approved
  → [THIS SKILL] Dispatch plan reviewer subagent
  → For plans with >15 tasks: review per-chunk
  → Issues found? Fix PLAN.md → re-dispatch reviewer
  → Approved? → Phase 5: Implement